In a spherical center-type processing machine, the spherical lens surface of a spherical-surface lens retained in a lens holder is pressed with a prescribed pressing force against a lens-processing dish (polishing dish), and in this state, the lens-processing dish is made to rotate and oscillate to precision-grind or polish the spherical lens surface, as is described in Patent Document 1. When precision grinding or polishing is performed on the spherical lens surface, the lens to be processed must be mounted as being centered between the lens holder and the lens-processing dish.
In other words, the lens must be mounted in a centered state in which a straight line joining the spherical centers of the spherical lens surfaces on both sides of the lens coincides with a straight line joining the spherical center of the spherical-surface-shaped lens-retaining surface of the lens holder and the spherical center of the spherical-surface-shaped lens-processing surface of the lens-processing dish. Lateral movement of the lens being processed must also be prevented so that the lens can be processed while remaining centered.
Therefore, an edge receiver is provided to the lens holder so as to enclose the outer peripheral edge of the lens-retaining surface. When the lens is retained in the lens-retaining surface, the edge, which is the lens circle's outer peripheral end surface, fits into the inner peripheral surface of the edge receiver, and the lens will be centered relative to the lens holder by the edge receiver.
Edgeless lenses can also be processed. In the case that an edgeless lens will be processed, there must be an operation such as affixing the lens to the lens-retaining surface of the lens holder with the lens centered.
Patent Document 1: JP 5453459 B